Abstract 12381: De Novo Multiple Myeloma in a Patient With Transthyretin Amyloid Cardiomyopathy

Abstract

Background: The development of de novo multiple myeloma in a patient with transthyretin amyloid cardiomyopathy (ATTR-CM) is rare and is often associated with poor prognosis. Early and definitive diagnosis is crucial to improve survival. Case: A 63-year-old male was evaluated for heart failure. He had a history of hypertension, sick sinus syndrome status post dual chamber pacemaker, non-sustained ventricular tachycardia requiring ablation in addition to bilateral carpal tunnel syndrome, spontaneous biceps tendon rupture, and lumbar spinal stenosis. Transthoracic echocardiogram showed progressive severe left ventricular hypertrophy with a septal thickness of 2.0cm with a normal left ventricular ejection fraction. Decision-Making: Given his history, an amyloid evaluation was performed. Serum and urine assessment for light chain amyloidosis revealed elevated kappa free light chains with kappa/lambda free light chain ratio of 19.30. Bone marrow biopsy at that time showed normocellular bone marrow with less than 3% plasma cells. An abdominal fat pad biopsy was inconclusive. A cardiac MRI was unobtainable given non-compatible pacemaker leads and a technetium-99m pyrophosphate scintigraphy was deferred given his abnormal light chains. An endomyocardial biopsy was performed and revealed wild-type ATTR deposition by mass spectrometry. Serum genetic test confirmed the absence of TTR gene mutation. The patient was started on Tafamadis. Six months later, he was noted to have progressive elevation in kappa free light chains on serial evaluation and underwent a repeat bone marrow biopsy. This showed plasma cell myeloma with 25-30% marrow cellularity and flow cytometry consistent with kappa light chain multiple myeloma. He was started on Daratumumab, Lenalidomide, and Dexamethasone. This resulted in normalization of his free light chain ratio and morphologic remission on repeat bone marrow biopsy. Conclusion: In patients who are found to have monoclonal gammopathy, an endomyocardial biopsy is crucial to evaluate for amyloid cardiomyopathy. These patients should also be monitored for the progression to multiple myeloma.